Soon after the Iroquois Theater Fire
(1906), the Rhoades Opera House Fire (1908) and the Triangle Shirtwaist
Fire (1911),1 the engineering and building code communities
in the United States began to consider the movement of people subsequent
to an unwanted fire. As a response, the National Fire Protection
Association (NFPA) formed the Committee on Safety to Life in 1913. Among
the committee recommendations at the1914 NFPA Annual Meeting were
building exit and stair requirements, including sufficient stair width
so that the entire population could, standing still and as closely
packed as possible, fit and take refuge in the stairs,2 which
explains why the U.S. national model codes design exits for capacity
and why the capacity is based on the population of a single floor. The
exit was sized to store people, motionless within the protected exit
enclosure, such that the population of one floor will fit within one
flight of the stair, with each person in a space 0.6m (22 in) wide and
standing on every other step.3 By the 1930s, more
sophisticated concepts for evacuation (e.g., flow rate for occupants
leaving the building) were being developed. These concepts, along with
the now-ubiquitous 1.2 m (44 in) stair width, were documented in 1935 by
the National Bureau of Standards (NBS, now NIST) report Design and
Construction of Building Exits.4 The landmark 1935 NBS report
substantiates recommendations for exit system design based on surveys
distributed to practicing architects, field inspections, citations to
previous investigations as far back as 1909, as well as simple
observations of exits and exit component usage during rush-hour and fire
drill evacuation conditions for contemporary building designs. These
recommendations constitute the primary basis for current egress
requirements, though modifications have resulted from large-loss
incidents, as well as subsequent research (e.g., Templar, 5 Pauls, 6 Predtechenskii and Milinskii,7 and Fruin8)

In addition to stairs, the idea of
leveraging the capacity of the elevator system to enhance occupant
safety has been long-discussed. Both the aforementioned 1914 NFPA
Proceedings and the 1935 Design of Building Exits document discuss the
use of elevators for egress from tall buildings, possibly related to the
observation that some evacuees in the Triangle Shirtwaist Fire used
elevators to evacuate. In 1974, Bazjanac proposed using elevators to
evacuate during fire emergencies9 and presented calculations in 1977.10 The NFPA Life Safety Code (LSC) considered the issue in the 1970s, including a detailed list of problems with using the elevators as fire exits.11 The
LSC Subcommittee on Means of Egress subsequently passed elevator egress
provisions in the late 1970s (Section 5-12 proposal), but the action
was overruled by the membership attending the association's annual
meeting.12

In anticipation of the Americans with Disabilities Act
(which required access to buildings but largely neglected consideration
of emergency egress for persons with disabilities), a consortium,
including NFPA, the American Society of Mechanical Engineers (ASME) and
the Council of American Building Officials (CABO) sponsored a symposium
on elevators and fire in Baltimore, MD, in 1991.12, 13 NIST held a workshop in 1992 with the research community and elevator industry.14 ASME hosted a follow-up workshop in 1995.15 Recently,
significant progress has been made regarding the use of elevators for
egress, which will be discussed later in this article.

While verification and validation of
behavioral theory lags the development of people movement
characteristics, there are links between human behavior and building
codes. Assembly occupancies, for example, require 50% of the required
exit width to be located at the primary entrance since occupants
consistently exit buildings preferentially by the exits through which
they entered the building. While building codes, models and technologies
have evolved over many years, current design is not immune from
large-loss events or inefficiencies.

THE PRESENT SITUATION

For 2005, NFPA estimated that the total
burden of fire in the United States was between $267- 294 billion
(U.S.), or roughly2 to 2% of U.S. gross domestic product.16 Direct costs, broken out by component:

Building costs for fire protection, $46 billion;

Estimated monetary equivalent for the deaths and injuries due to fire, $42 billion;

Other economic costs, 40 billion;

The cost of career fire departments, $31
billion (the value of donated time from volunteer firefighters was not
included) ;

Provision of adequate egress provisions
(or failure to) contributes directly to the two largest direct costs:
installed fire protection and deaths and injuries. Indeed, at first
glance, egress is a life safety problem. Of all victims of structural
fires in the United States (roughly 2,800 per annum17), Hall indicates that one-fourth perish during evacuation.18 Therefore,
as many as 700 persons could be saved by egress design improvements. Of
these, approximately 150 would be in non-residential buildings, nearly
100 would be in apartment buildings and the remainder would be in one-
or two-family residences.

In order to improve the outcomes of residential
fire scenarios by improving the time to escape, the design of a typical
one- and two-family residences egress system should be considered. The
configuration of common two- or three-story residences requires
occupants to egress down to the first floor via an unprotected path.
Even in a single-story home, the configuration of the sleeping areas is
often such that occupants must egress through the area of fire origin
due to a dead-end corridor arrangement serving the bedrooms.

However,
fire fatalities may be more cost-effectively addressed by reducing the
number of fires and the resulting fire growth and spread.

Egress design technologies could
significantly reduce the annual life loss in non-residential buildings.
Improvements in signage, markings and lighting led to great reductions
in egress time from One World Trade Center on Sept. 11, 2001, compared
to the 1993 bombing and subsequent evacuation of the same building. On
Sept. 11, 2001, self-evacuation and the use of elevators in World Trade
Center Building Two (before it was struck by an airplane) led to several
thousand lives saved.19 Validated egress models that
accurately convey the expected range of evacuation times are on the
critical path to performance-based design (PBD); however, the present
dearth of usable input or validation data renders model output subject
to uncertainty. If validated egress and fire models with a broad range
of appropriate input data were available, an Australian study estimated
the potential impact of PBD at 0.5% of the total cost of construction.20 This could translate to national savings of roughly $5 billion in the United States.

While there are reasons to believe that
egress research and implementation will achieve significant reductions
in the national fire burden, there are also reasons to wonder whether
the problem is increasing. Aggressive building designs, changing
occupant demographics (an aging population and an obesity epidemic in
the United States and other developed countries) and consumer demand for
higher-performing and more energy-efficient systems have pushed egress
designs beyond the traditional stairwell-based approaches. While
precious little underlying data exists for traditional stair-based
egress systems, there is virtually no technical foundation for
performance and economics of emerging systems such as occupant
evacuation elevators, active direction egress signage or mass
notification technologies.

Egress Modeling
Evacuation calculations are increasingly
becoming a part of life safety analyses. In some cases, engineers are
using algebraic (hand) calculations to assess life safety, and in
others, computational evacuation models are being used. Hand
calculations usually follow the equations given in the Society of Fire
Protection Engineers (SFPE) Handbook of Fire Protection Engineering21 to
calculate mass flow evacuation from any location within the building.
The occupants are assumed to be standing at the doorway to the egress
component on each floor as soon as the evacuation begins. The
calculation focuses mainly on points of constriction throughout the
building (commonly the door to the outside, transitions between egress
components, or where different paths merge) and calculates the time for
the occupants to move past these points and to the outside. To achieve a
more realistic evacuation calculation, or a more efficient solution,
engineers have been using evacuation computer models to help assess key
egress design aspects. Currently, there are dozens of evacuation models
from which to choose, with various underlying bases, interfaces,
characteristics and applications. These models can range from a
numerical implementation of the hand calculations (thus having the same
limitations as the hand calculations) to models that have complex
equations and occupants with simulated decision-making.

There have been several recent trends in
egress model features that have increased the complexity of the
evacuation models overall.22

More models are including behaviors and
decision-making capabilities for the simulated occupants.

The attributes and decisions of the
occupants are often defined in a probabilistic fashion that requires
multiple iterations of each simulation to determine the range of
expected occupant evacuation times and movement speeds.

The majority of the available models
simulate movement on a continuous grid. The continuous grid is more
complex, since occupants are not assigned to a specific cell but can
instead be located anywhere in the building.

Modeling input is now more complex,
including incorporation of fire effects into the simulation and CAD
drawings' import features.

Nearly all current models provide
three-dimensional visualization of people movement and building
geometry. While this change does not improve the underlying quality of
the numerical results, it better enables insight into the evacuation
process.

While egress models continue to develop
more complex features and formulations, the underlying technical basis
for modeling (which includes both rigorous, science-based theory and
publicly available, well-documented data sets) has progressed more
slowly. The root basis for many models continues to be a handful of
historic datasets.23 As a result, rigorous verification and
validation of egress models is typically lacking and is well behind the
reliability of fire modeling predictions.

Human Behavior and Emergency Management
Traditionally, evacuation models and
users have often made assumptions and simplifications about occupant
behavior (i.e., what people do during evacuations) that can be
unrealistic and are likely to produce inaccurate results. Behavioral
research in the fire community has been conducted, including development
of theory (e.g., Sime24 and Bryan25) and data (e.g., Paulsen, 26 Keating and Loftus, 27 and Proulx28).

Kuligowski is developing a comprehensive
conceptual model of occupant behavior during building fires by
describing the current state of evacuation modeling of human behavior in
fire, identifying gaps in current behavioral techniques, and outlining a
general process model for occupant response to physical and social cues
in a building fire event.29 A theory should predict the
variety of behaviors performed by occupants in a building fire (e.g.,
seek information, warn, rescue and prepare). Because occupants' actions
vary based on their interpretations of and interactions with their
physical and social environments, it is crucial to develop a theory of
occupant behavior in building fires based on social, psychological and
group behavioral processes.30

Social scientific theory has acknowledged
for more than 70 years that human action or response is the result of a
process. Instead of actions based on random chance or even actions
resulting directly from a change in the environment, an individual's
actions are frequently the result of a decision-making process.31 Research
in disasters, based on social scientific theory, has led to the
development of social-psychological process models for public warning
response (e.g., Mileti and Sorensen32 and Perry, et al.33).
These models specify that people go through a process of specific
phases, including receiving the warning, perceiving a threat,
personalizing the risk, and deciding upon a plan of action to protect
people and property in response to a disaster.31 Additionally, researchers of fire evacuations (e.g., Bryan,34 Feinberg and Johnson,35 and Breaux, et al.36)
have shown that a process involving the phases of recognition and
interpretation of the environment influence occupant actions. In these
process models, specific cue- and occupant-related factors influence the
outcome of each phase of the process (e.g., whether the person hears
the warning or interprets the situation correctly). Cue-related factors
are described later in this paper. Occupant-related factors include
previous experiences, knowledge about disasters and training. Research
remains inconclusive about the direct effects of demographics (e.g.,
gender, age, income, education, race and marital status) on the
decision-making process. An understanding of the decision-making process
and its influential factors can be developed into a conceptual model to
predict the types of individual behaviors that are likely to occur in
building fires.

People Movement Data
As part of a program to better understand
occupant movement and behavior during building emergencies, NIST has
been collecting stair well movement data during fire drill evacuations
of multi-story buildings. These data collections are intended to provide
a better understanding of this principal building egress feature and
develop a technical foundation for codes and standards requirements. To
date, NIST has collected fire drill evacuation data in 11 office,
municipal and residential building occupancies ranging from six to 62
stories in height that have included a range of stairwell widths and
occupant densities. The goal is to provide a solid technical basis for
the required number and width of stairs in tall buildings. As the data
are converted to spreadsheet and quality control is completed, it is
being made available on a public website (http://www.nist.gov/el/fire_research/egress.cfm) for use by the fire protection and egress communities.

Additionally, to support standardization
of egress data sets, Gwynne has developed a standardized format for
archive data.37 In addition to improving the ability of the
user to parse and understand the data set, standardization will enhance
the quality of future data collections. By reviewing the standard data
reporting and storage format prior to data collection, researchers are
provided with a checklist of data collection elements that may increase
the number and quality of the collected data elements.

Elevators
Elevators may become a significant
component of evacuation from tall buildings in the near future and
should dramatically reduce the overall building evacuation time for
high-rise buildings when used in conjunction with stairs. Recent code
provisions were included in both the International Building Code38 (IBC) and the Life Safety Code.39 Subsequent
to the World Trade Center disaster in 2001, a collaborative effort
between ASME, NIST, International Code Council (ICC), NFPA, U.S. Access
Board and the International Association of Firefighters (IAFF) was
launched to reexamine the use of elevators.40 This resulted
in quarterly task group meetings to develop technical requirements for
occupant and firefighter use of elevators during fire emergencies.

A recent economic analysis examined the
first- and life-cycle costs for two prototypical office buildings using
the IBC alternatives. For new high-rise buildings over 128 m (420 ft)
high: (1) an additional exit stair is a cost-effective alternative to
the installation of occupant evacuation elevators on a first-cost basis;
and (2) occupant evacuation elevators are a cost-effective alternative
to the installation of an additional exit stair on a life-cycle cost
basis when rental rates are high and discount rates are low.41 Public
policy should then balance the economic considerations of stairs versus
elevators in the context of potentially significant egress performance
benefits afforded by use of occupant evacuation elevators.

THE FUTURE

A Consensus Research Agenda
In order to maximize the effectiveness of
limited resources, the egress community would benefit greatly from a
prioritized, consensus-based research agenda. The first five proposed
research initiatives discussed here were initially presented at the 5th
International Conference on Pedestrian and Evacuation Dynamics in
Gaithersburg, MD, in March 2010.42 By marshalling limited
resources towards collectively or systematically addressing significant
issues, the field can mature more rapidly and maximize the impact of
future efforts. A consensus research agenda approach has been successful
in other disciplines at guiding both researchers during the proposal
development stage, as well as agencies or organizations that fund
research. If a research proposal has the magnitude of the problem
validated by an objective, traceable publication linked to the consensus
of disciplinary experts, confidence in successful outcomes is increased
in both funding and receiving parties. One example of a successful
consensus research agenda is the Firefighter Life Safety Initiatives.43 A
representative cross-section of fire service leaders gathered and
achieved consensus on 16 priority research needs. The document
subsequently guided grant applications and awards from agencies of the
U.S. federal government. A second example of a research agenda includes
the six research priorities identified in Grand Challenges for Disaster
Reduction,44 a document developed by the U.S. National
Science and Technology Council's Subcommittee on Disaster Research.
Finally, while the Rethinking Egress workshop in 2008 did not produce a
consensus research agenda, the proceedings document produced several
hundred ideas for innovative technologies that may improve building
evacuation.45

1: Develop and validate a comprehensive theory that predicts human behavior during pedestrian or evacuation movement
Ball bearing and other physics-based
models are inadequate to predict the full range of possibilities for
evacuation scenarios. People make predictable, though varied, decisions
when confronted with evolving information and conditions, rather than
behave like robots or inanimate objects responding to fixed laws of
nature. The first step will require theoretical models, several variants
of which already exist. The second step will be to develop methods
(beyond observational) that can validate the components of the
theoretical models. The final step will be to integrate the theoretical
models into the egress models.

2: Create a comprehensive database of actual emergency data
The field of evacuation has developed
largely on the foundation of a small number of (30+year-old) data sets.
Virtually no information exists that examines the applicability of the
existing data for real emergency scenarios. A comprehensive database
that catalogues the progress and outcomes for real emergency incidents
(the crucible in which theory and drills are tested) is a necessary
condition for acceptance and validation of all knowledge in the field.
Establishment of the database will require methods to document initial
conditions, incident environmental conditions, and occupant information
and responses, both during the incident and post-incident. Even if the
researchers knew when and where an event would occur, the infrastructure
to collect, analyze and archive the data has not yet been developed.

3: Embrace variance
The vast majority of current generation
models are deterministic. Building evacuations are highly stochastic
processes. If one were to evacuate the same building with the same
people starting in the same places on consecutive days, the answers
could vary. In addition, the number of people present within a building
(and the mobility performance of individuals) can vary day-to-day or
within a day. The egress community must move away from terms such as
average and evacuation time, and adopt tools and techniques that manage
distributions of inputs and outputs. Probabilities should be attached to
the distributions and a discussion of acceptable risk should take place
in every nation and community.

4: Integrate results of evacuation models with fire models to enable accurate and reliable performance-based design
The calculation of Available Safe Egress
Time (ASET) is well ahead of any reliable and validated prediction of
Required Safe Egress Time (RSET). The interaction of the occupants with
the constraints imposed by the emergency (e.g., people evacuating
through smoke) has implications for a host of disciplinary contributions
(toxicology, psychology, sociology, architecture, engineering,
mathematics, to name a few). Scenarios equivalent to design fire
scenarios should be developed for building evacuation. In addition, both
of these concepts are distributions (as discussed in challenge No. 3),
and methods for combining the outcome distributions in a meaningful way
that can be understood by the design and regulatory communities for safe
and cost-effective building design must be developed prior to
realization of the full potential for performance-based design.

5: Embrace technology
Given the paucity of data on simple
concepts (such as stairs), it should not surprise anyone that virtually
no data exist for use of technology to improve building evacuation
effectiveness. Technologies exist and are being developed based on
integration of building sensor information, communication technologies,
active signage and movement technologies, such as elevators, escalators
and alterative escape devices. For these technologies, there are
virtually no experimental data, incident data, theoretical models or
computational algorithms to encourage adoption of more effective
strategies. The egress community must lead the way in enabling the
enhancements by proactively seeking and developing technologies through
data and models.

6: Model Validation
In addition to conducting research to
establish a strong technical foundation for egress, the fire protection
engineering community (a primary user of egress models) should establish
a formal round-robin assessment of egress models. Validation efforts
are few and largely undertaken using proprietary datasets (not in the
public domain) by model developers who are familiar with the validation
data, including the outcome. The round-robin should be conducted using
several types of models (assuming that the model is applicable to the
scenario), across several different scenarios and by general (though
knowledgeable) users, as well as expert users (possibly including
developers). Ideally, the process would be consistent with a model
validation standard. A round-robin assessment of egress models meeting
these criteria will establish several key outcomes:

Variance of model output given identical inputs for several models

Variance of model output for different users of the same model given similar initial information

Benefits of underlying formulation and
various sub-models relative to accuracy and simulation time

Although it represents a significant
community investment, given the significant life-safety and economic
considerations that result from egress model simulations, it would seem
prudent to have an objective assessment of inter-model and inter-user
capabilities and outcomes.

EGRESS RESEARCH PRIORITIES

A general human behavior model with a theoretical foundation and numerical validity;

A database archiving actual building emergency evacuations;

Methods to embrace the stochastic nature of inputs and outcomes in building evacuation;

A validated method to integrate
distributions of egress calculations with fire hazard calculations;

Adoption of technology for people movement, data collection and within modeling constructs;

Round-robin assessment of egress model and user capabilities.

Jason D. Averill, Erica D. Kuligowski and Richard D. Peacock are with the National Institute of Standards and Technology.

Bukowski,
R. W. Emergency Egress From Buildings. Part 1. History and Current
Regulations for Egress Systems Design. NIST Technical Note 1623; January
2009.

NBS.
Design and Construction of Building Exits. National Bureau of Standards
Miscellaneous Publication M151. National Bureau of Standards.
Washington, DC. October 10, 1935. Document can be found at: http://www.nist.gov/el/fire_research/egress.cfm.

Pauls, J. Building Evacuation: Research Findings and Recommendations. Fires and Human Behaviour. John Wiley and Sons, New York. 1980.

Predtechenskii,
V. and Milinskii, A. Planning for Foot Traffic Flow in Buildings.
Published for The National Bureau of Standards, Amerind Publishing Co.,
1978 (translated from the Russian publication which appeared in 1969,
Stroizdat, Publishers, Moscow, 1969).

Kady, R., Gwynne, S. and Davis, J. A Review of the Sources of Occupant Performance Data Used in Building Evacuation Models. In Proceedings of Human Behaviour in Fire Symposium. Interscience Communications, London, July 2009.

Sime, J. Escape from Building Fires: Panic or Affiliation? Ph.D. Dissertation, University of Surrey, UK. 1984.

Bryan, J., Smoke as a Determinant of Human Behavior in Fire Situations. University of Maryland, College Park. 1977.

Averill, J. Five Grand Challenges in Pedestrian and Evacuation Dynamics. In Proceedings of the 5th International Conference on Pedestrian and Evacuation Dynamics. Gaithersburg, MD. March 8-10, 2010. Springer, publication pending.

Report
of the National Fire Service Research Agenda Symposium, National Fire
Service Research Agenda Symposium. United States Fire Administration.
Emmitsburg, MD. 2005.

Grand
Challenges for Disaster Reduction. A Report of the Subcommittee on
Disaster Reduction. National Science and Technology Council. Washington,
D.C. 2005.

About SFPE

SFPE is a global organization representing those practicing in the fields of fire protection engineering and fire safety engineering. SFPE’s mission is to define, develop, and advance the use of engineering best practices; expand the scientific and technical knowledge base; and educate the global fire safety community, in order to reduce fire risk. SFPE members include fire protection engineers, fire safety engineers, fire engineers, and allied professionals, all of whom are working towards the common goal of engineering a fire safe world.